1. Field of Invention
The field of the currently claimed embodiments of this invention relates to magnetic resonance imaging (MRI) systems and methods, and more particularly to MRI systems and methods that include motion correction and/or accelerated processing for increased frame rates.
2. Discussion of Related Art
The advantageous use of magnetic resonance technology in providing safe, rapid images of a patient has long been known. It has also been known to employ resonance technology in producing chemical shift spectra to provide information regarding the chemical content of a material.
In a general sense, magnetic resonance imaging involves providing bursts of radio frequency energy on a specimen positioned within a main magnetic field in order to induce responsive emission of magnetic radiation from the hydrogen nuclei or other nuclei. The emitted signal may be detected in such a manner as to provide information as to the intensity of the response and the spatial origin of the nuclei emitting the responsive magnetic resonance signal.
In general, imaging may be performed in a slice or plane or multiple planes or three-dimensional volume with information corresponding to the responsively emitted magnetic radiation being received and conveyed to a computer which stores the information in the form of numbers or data corresponding to the intensity and phase of the signal. The pixel value may be established in a computer by employing Fourier Transformation (FT) which converts the signal amplitude and phase as a function of time to signal as a function of frequency, which translates to spatial position within the volume. The signals may be stored in the computer and may be delivered with or without enhancement to a video screen display, such as a cathode-ray tube, for example, wherein the image created by the computer output will be presented through black and white presentations varying in intensity, or color presentations varying in hue and intensity. See, generally, U.S. Pat. No. 4,766,381.
Recently, MRI technology has been used in connection with endoscopes, where a stream of images is provided from the viewpoint of an MRI probe introduced internally into the imaging volume1. For example, the probe may be moved through orifices, or blood vessels, or tissues in a human body with the intrinsic high sensitivity to pathology that characterizes MRI. However, the probe advancement has been limited by scan time which renders the images sensitive to motion artefact.
Current speeds for intravascular (IV) MRI and MRI endoscopy1 are limited to ˜2 frames/s at 3T, although it will be appreciated that higher and lower frame rates are often desirable to enhance particular aspects of the responsive signals, such as image contrast or flow sensitivity etc. In any case it will be appreciated that high-resolution (e.g. ˜50-500 μm) images may be susceptible to degradation by physiological and random motions when their amplitudes are of the order of mm at time-frames shorter than the scan period.
Compressed sensing has been previously proposed and implemented to speed up conventional MRI and angiography2-7. It is also used in other image applications involving data and image compression. However, it has not been adapted for use in MRI endoscopy with either radial projection or Cartesian MRI pulse sequences, nor in conjunction with internal MRI detectors.
Therefore, there remains a need for improved MRI systems and methods for motion correction and/or accelerated processing for increased frame rates.